We had a bunch of issues sneak into the codebase that made it impossible

to set up or run the release-7.1.x branch against Python 3.8. This

change fixes them up:

Our pyproject.toml file required setuptools>=77, but the last release

  that supports 3.8 was 75.
Once that was fixed, I was getting errors about the format of the

  license lines.
There were several few places where type annonations were getting

  evaluated, primarily in generics, TypeAliases, and Pydantic models.

  We had a number of places where we had more-modern syntax (type[...],

|-syntax for unions) or were getting things from collections.abc

  that needed to come from typing because the collections versions

  don't support subscripts for 3.8.
Some of the new hosting services stuff was using str.removeprefix(),

  which was introduced in Python 3.9.

Set up a Python 3.8 environment and ran unit tests.